SYNAPSES AS ASSOCIATIVE MEMORY ELEMENTS IN THE HIPPOCAMPAL-FORMATION
SYNAPSES AS ASSOCIATIVE MEMORY ELEMENTS IN THE HIPPOCAMPAL-FORMATION
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DOI：
10.1016/0006-8993(79)91003-5
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发表时间：
1979-01-01
期刊：
影响因子：
2.9
通讯作者：
STEWARD, O
中科院分区：
文献类型：
--
作者：
LEVY, WB;STEWARD, O
对同侧和交叉的内嗅皮质（EC）通路至齿状回（DG）的突触之间的长时程增强（LTP）和联合相互作用进行了分析。在麻醉大鼠中，对一条EC - DG通路的条件刺激可靠地在同侧突触引发LTP，而对侧DG的侧支交叉通路的突触则不表现出LTP。在条件刺激同侧的DG中，来自对侧未自身受到条件刺激的汇聚交叉通路未能表现出异突触LTP。这些结果与导致LTP的变化的特定突触定位相符，并表明必须激活一定数量的关键突触才能观察到LTP。虽然单独对交叉的EC - DG投射进行条件刺激时从未表现出LTP，但在某些情况下交叉输入可以被增强。具体而言，通过对双侧EC几乎同时进行条件刺激对同侧和对侧输入进行配对条件刺激，会导致交叉系统中的LTP。这种联合诱导的交叉系统的LTP可通过随后单独对同侧系统进行条件刺激而逆转。即使在阻止通过EC的神经回路的损伤之后，使用配对和非配对刺激程序也可能出现连续的增强和去增强序列。这些结果被解释为具有擦除能力的赫布型突触的证据。这种突触类型不适合没有附属电路的经典条件反射，但适用于其他形式的联想学习。
Long term potentiation (LTP) and associative interactions between synapses of the ipsilateral and crossed entorhinal cortical (EC) pathways to the dentate gyrus (DG) are analyzed. In the anesthetized rat, conditioning stimulation to 1 EC-DG pathway reliably elicits LTP at the ipsilateral synapses, while the synapses of the collateral, crossed pathway to the contralateral DG do not exhibit LTP. In the DG ipsilateral to the conditioning stimulation the convergent crossed pathway from the contralateral side, which had not been itself conditioned, failed to exhibit heterosynaptic LTP. These results are consistent with a specific synaptic localization of the changes responsible for LTP, and suggest that some critical number of synapses must be activated to observe LTP. While the crossed EC-DG projection never exhibited LTP when conditioned alone, the crossed input could be potentiated under certain circumstances. Specifically, paired conditioning of ipsi- and contralateral inputs by nearly simultaneous conditioning stimulation of the EC bilaterally results in LTP in the crossed system. This associatively induced LTP of the crossed system can be reversed by subsequent conditioning of the ipsilateral system alone. Successive potentiating and depotentiating sequences are possible using paired and non-paired stimulation procedures even after lesions which prevent neural loops through the EC. The results are interpreted as evidence for a Hebb type synapse which has the capability for erasure. This synaptic type is not appropriate for classical conditioning without appendant circuitry, but is suited for other forms of associative learning.